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Sacral stress fractures are uncommon injuries that are associated with repetitive load-bearing activities. The authors describe a 23-year-old male cross-country runner who presented with low back and buttocks pain. Radiographic findings were unremarkable, but a hop test identified a sacral stress fracture. The patient was instructed to stop running and to take calcium and vitamin D supplements. Four months later, his symptoms completely resolved and he began running again. The authors also present a review of the literature, which revealed that patients with sacral stress fractures are likely to have normal neurologic examinations and full active range of motions. However, they will likely describe discomfort with passive hip flexion. The authors recommend the hop test for patients with this type of history and these physical examination findings. If a sacral stress fracture is found, treatment regimens should consist of 4 to 6 weeks of rest with gradual return to activity.

Sacral stress fractures are uncommon injuries characterized by low back and buttocks pain and typically present in individuals who participate in endurance, load-bearing activities such as military or band marching, running, and aerobic exercise.1-18 Individuals with this type of injury return to partial activity levels after 4 to 6 weeks of rest. Non-load-bearing activities and eventually full participation are resumed in 5 months to 1 year. Findings from a review of the case report literature suggest that patients with sacral stress fractures have followed similar evaluation, treatment, and return-to-participation parameters. A standardized differential diagnosis may aid in quicker diagnosis of sacral stress fractures.

The cause of a sacral stress fracture can vary based on the health and activity of the patient. Amenorrhea, fatigue, and overuse of the lower extremities are common characteristics of individuals with sacral stress fractures.1-20 However, prolonged strenuous activity with repetitive lower-extremity loading has been described in almost all of the reported cases. Stress fractures are most common in the lower extremities of patients, particularly in the tibia and femur.5,6 Stress fractures can be related to insufficiency (low bone mineral density), fatigue, or both.7 Stress fractures that occur in patients with normal bone density are typically due to mechanical overload and repetitive stress, which increase osteoclastic activity and weaken the bony structure.7,13

Clinicians should be aware of sacral stress fracture commonalities, including etiology, treatment, and return-to-participation parameters. We present a case of a man who was a cross-country runner with a sacral stress fracture. We also include a report of the literature and highlight similarities among cases for better diagnostic efficiency and treatment plans.

Report of Case

A 23-year-old white man presented to the athletic training room at his university with a complaint of discomfort on the right side of his lower back and buttocks. He was examined by a physical therapist. The patient had been participating in year-round collegiate cross-country training, and the discomfort had occurred during a 4-mile light run the day before presentation. The patient had been running 84 to 102 miles per week for 3 months. After the 4-mile run, the patient completed a workout consisting of 1000-m hill repeats (ie, running up and down hills) on grass terrain and noted a slightly elevated amount of discomfort in the affected area.

The patient described a deep, mild, “shooting” pain unilaterally on the right side of his posterior sacrum. The patient also described pain in his lower back consistent with piriformis and gluteus maximus muscle strain. Pain was reproducible on palpation at the right ischial tuberosity. Tightness and guarding in the right hamstring were evident with passive hip flexion. The patient had a spasm of the gluteus maximus muscle inferior to the iliac crest. In addition, visual inspection of the position of the medial malleoli revealed a slight leg length discrepancy. The physical therapist applied moderate stretching to both legs and muscle energy techniques to the patient's adductor and abductor hip muscles (isometric contraction for 10 seconds, repeated 3 times for each muscle). With the patient in a lateral recumbent position, the team osteopathic physician (T.A.) performed lumbar and sacroiliac mobilization. The right side of the innominate bone had a superior shear, which the physician managed directly with high-velocity, low-amplitude, or HVLA, technique with immediate resolution. The patient was instructed to retrain the gluteus maximus muscle by extending his right leg while in a prone position. Strengthening of the hip internal and external rotators was accomplished with stabilization of the sacroiliac joint. Stabilization was provided by the patient's body weight to “re-set” the pelvis by using 10-second isometric contractions of the hip adductor and hip abductor muscles (3 repetitions for each muscle group), which minimized the functional leg length discrepancy.

The patient's pain persisted, and he returned to the athletic training room the next morning (day 2) and was evaluated by the physical therapist. An extremely pronounced leg length discrepancy was discovered during pelvic rotation, which the physical therapist managed using muscle energy techniques. With the patient in a supine position, the physical therapist performed isometric contraction to the patient's abduction and adduction hip muscles to flex his hip and knees and to improve the leg length discrepancy. The patient cross-trained that afternoon instead of running.

On day 3, the patient's pain level was reduced, so he attempted to complete the afternoon light run. Pain during the first mile forced the patient to stop and return to the athletic training room, where he was immediately referred to the team osteopathic physician. A physical examination indicated sacroiliac joint tenderness with associated left-on-right sacral torsion, lumbar spine segmental rotation, point tenderness on the right ischial tuberosity, and decreased flexibility in the right hamstring muscle.

The physician used an indirect functional method to manage the left-on-right sacral torsion. Re-examination revealed a level sacral base and resolution of symptoms. Dysfunction of the bilateral hamstring muscles was managed directly by using muscle energy technique. Hamstring muscles in both legs were taken to the edge of restrictive barrier, and the patient applied an isometric contraction to his hip flexor and hamstring muscles 1 leg at a time for 10 seconds. After each contraction, passive motion of the hamstring muscle was taken to a new edge of restrictive barrier, and the contraction was repeated. This process was repeated 3 to 5 times on each leg until either somatic dysfunction was no longer present or full range of motion was noted. The transverse tarsal joint of the right foot was restricted in pronation and internal rotation. This was managed directly with muscle energy technique by using patient-applied isometric contractions for 10 seconds. This process was repeated 2 times, at which point somatic dysfunction was no longer present. Spinal level L5 was noted to be extended, rotated left, and side bent left. This was managed indirectly by using a functional method, which improved somatic dysfunction. The physician also applied interferential electric stimulation at the proximal hamstring by using interferential current (100% scan setting; range, 80-150 Hz) while applying ice to the area to reduce inflammation.

Approximately 4 days after the initial evaluation, the patient's pain level had not decreased, and he was again referred to the team physician. The physician did not find any new somatic dysfunctions. To alleviate the patient's pain, the physician injected a mixture of 40-mg triamcinolone acetonide (1 mL), 0.5% bupivacaine hydrochloride (1 mL), and 1% lidocaine hydrochloride (1 mL) into the right sacroiliac joint. The patient had immediate relief and was able to compete the next day in the conference championship race with moderate pain during the race but severe pain during the cool-down jog.

The patient returned to the athletic training room 14 days after the initial evaluation, at which point the physical therapist treated the patient with electrical stimulation, ice, and muscle energy techniques to decrease pain near the sacroiliac joint and the hamstring muscle origin. After approximately 7 days of conservative treatments, the patient revisited the team physician (24 days from the initial evaluation). The physician reassessed the patient's alignment and flexibility and requested that the patient jump up and down, a technique described in the literature as the hop test.21 This test reproduced pain in the affected area, which raised concern for a potential stress fracture, because the pain had not been present at the previous examination. On the basis of the location of the pain, the physician suspected the sacrum or ilium as the location of potential fracture. Because of the rarity of sacral stress fractures in patients, particularly in men, the physician included a stress fracture of the neck of femur in the differential diagnosis based on a higher statistical probability.22

The patient was referred for radiography; pelvis, hip, and sacrum radiographs did not reveal any fractures. However, radiography often lacks the necessary sensitivity to identify sacral fractures; only 20% to 38% of fractures are evident in radiographs.23,24 The patient was also referred for magnetic resonance imaging (MRI) of the spine and pelvis. Results of the MRI of the lumbar spine without contrast material depicted the alignment of the lumbar spine to be within normal limits and revealed no suspicion of lumbar spine edema or signal intensity abnormality. The MRI findings of the pelvis revealed substantial edema and associated marrow changes along the right side of the sacrum, which were consistent with a nondisplaced sacral stress fracture. Inflammation was not visible outside the bone or in extension to the cortical surface, which indicated that the fracture was recent. The levels of inflammation in the associated surrounding soft-tissue structures were all within normal limits.

Blood test results revealed normal vitamin D and phosphorus levels. Findings from bone densitometry indicated that bone mineral density of the spine and bilateral femoral necks were within normal limits. The physician instructed the patient to stop running for approximately 4 months and to schedule follow-up visits to assess the progression of healing. The patient was permitted to continue regular daily activities but was instructed to avoid prolonged standing and to minimize walking. The patient was also encouraged to take the recommended dosage (2000 IU/d) of an over-the-counter calcium and vitamin D supplement, which he took for approximately 2½ months. The patient cross-trained with non-loadbearing activities (ie, swimming and biking) during this phase. Approximately 2½ months after the initial evaluation, the physician allowed the patient to begin fitness walking, pool running, and elliptical training. Four months after the initial evaluation, the patient began training again for cross-country distance running with a peak mileage of no greater than 60 miles per week. The patient supplemented his training with morning cross-training sessions to maintain cardiovascular fitness. At this time, the patient's pain had completely resolved.

Comment

A literature search of the US National Library of Medicine's PubMed database using the search term sacral stress fracture yielded 60 reported cases of sacral stress fractures (Table 1).1-18 In these cases, 57 of 60 individuals with sacral stress fractures initially presented with low back pain and diffuse buttocks pain, similar to the symptoms of the patient in the present case. In the 3 other cases, the signs and symptoms of a sacral stress fracture mimicked those of sciatica or vertebral disk dysfunction.25

Table

Reported Sacral Stress Fractures: Review of Evaluation and Treatment

Age, y

Sex

Activity

Symptoms

Special Tests

Treatment

Return to Participation

2212

F

Long-distance running (140 km/wk)

Buttocks pain

□ MRI

□ Rest

8 wk

□ Hop test

□ Diclofenac

□ Xylocaine injection

□ RTP as tolerated

1617

F

Volleyball

LBP

□ MRI

□ 3 weeks of rest

4 wk

□ FABER test

□ RTP as tolerated

349

F

Long-distance running

Asymmetry of the hip

MRI

NA

NA

149

F

“Enthusiastic” running

□ Sacroiliac joint pain

□ FABER test

NA

NA

□ Pain from load-bearing activity

□ Radiography*

□ CT

□ Bone scintigraphy

99

M

No history, gradual onset

Sacroiliac joint pain

□ Radiography†

NA

NA

□ MRI

□ CT

159

F

Gymnastics, softball

Sacroiliac joint pain

CT

□ NSAIDs

7 wk

□ Non–load-bearing activity, 7 wk

169

F

Long-distance running

□ Lumbosacral pain

□ Bone scintigraphy

Rehabilitation

8 wk

□ Buttocks pain

□ CT

21.4 (average)7

□ 12 F

Long-distance running

□ LBP

□ Bone scintigraphy

□ Non-load bearing activity 2 wk

NA

□ 9 M

□ Buttocks pain

□ Hop test

□ Pain from load-bearing activity

□ MRI§

□ Aquatics 4 wk

□ CT§

□ Gradual return to impact

□ MRI/CT§

□ Bone densitometry

□ Oral contraceptives for amenorrhea (9 F)

□ Treatment for osteopenia (7 F, 2 M) and osteoporosis (2 M)

1818

M

Military recruit

□ Groin pain

□ Radiography†

Bed rest

6 wk

□ Lateral thigh pain

□ Bone scintigraphy

□ CT

1818

M

Military recruit

Sacroiliac joint pain

□ Gaenslen test

Rest

3 mo

□ Bone scintigraphy

2018

M

Military recruit

□ Sacroiliac joint pain

□ Gaenslen test

Rest

2 mo

□ Femoral pain

□ Bone scintigraphy

Elderly4‡

10†

None (chronic inflammatory diseases present)∥

Sudden onset of LBP

□ Bone scintigraphy

NA

NA

□ CT

205

M

Long-distance running

□ Lumbosacral pain

□ Sacroiliac stress test

□ Rest 12 wk

3 mo

□ Sacroiliac joint pain

□ Hop test

□ Progressive strengthening program

□ Buttocks pain

□ Bone scintigraphy

□ Pain from load-bearing activity

□ CT

2111

F

Soccer

Sacroiliac joint pain

□ Bone scintigraphy

□ Rest, 4-6 wk

1 y

□ MRI

□ Rehabilitation

□ CT

2011

F

Basketball

LBP during sitting

□ Bone scintigraphy

□ NSAIDs

9 mo

□ MRI

□ Rehabilitation

□ CT

4511

F

Running

□ Groin pain

□ Bone scintigraphy

□ Rest

14 mo

□ LBP

□ MRI

□ Walking routine

□ CT

2211

F

Cross-country running

Sacroiliac joint pain

□ Bone scintigraphy

Rest

9 mo

□ MRI

□ CT

4111

F

Jogging

Buttocks pain

□ Bone scintigraphy

Rehabilitation

5 mo

□ MRI

□ CT†

1911

F

University mascot

□ Sacroiliac joint pain

□ Bone scintigraphy

Rest

Complicated by herniated disk at 13 mo after diagnosis

□ Buttocks pain

□ MRI

□ CT

2011

F

Cross-country running

□ Buttocks pain

CT

NSAIDs

5 mo

□ Sacroiliac joint pain walking

2111

F

Cross-country running

□ Hip pain radiated to lateral thigh and ischial tuberosity

□ Bone scintigraphy

NA

NA

□ MRI

□ CT

□ Exacerbation with load-bearing activity with single leg

202

M

Basketball

□ Buttocks pain

□ MRI

□ Rest

11 wk

□ Pain with load-bearing activity

□ Bone scintigraphy

□ Analgesia

2115

F

Cross-country running

□ LBP

Bone scintigraphy

□ Rest

2 y

□ Buttocks pain

□ Aquatics

□ Pain with walking

□ Sacral point tenderness

2115

F

Cross-country running

□ Buttocks pain with running

CT

□ Rest

NA

□ Aquatics

□ Sacral point tenderness

1715

NA

Multiple sports¶

□ LBP

Bone scintigraphy

Rest 6 wk

12 wk

18-4914‡

□ 1 F

Long-distance running

□ LBP

□ CT

NA

NA

□ 3 M

□ History of disk disease

□ Bone scintigraphy

□ MRI

341

F

Long-distance running

□ Sacral pain

□ FABER test

□ Manual therapy

8 wk

□ Sacral plexus point tenderness

□ MRI

□ Rest

1912

F

Long-distance running

□ LBP after running

CT

□ NSAIDs

9 wk

□ Sacroiliac joint pain

□ Rest, 6 wk

□ Gradual return

*Findings revealed sclerosis.

†Findings were unremarkable.

‡Descriptors were lacking.

§Nine stress fractures were confirmed with MRI, 9 were confirmed with CT, and 2 were confirmed with MRI and CT. Results of 6 MRIs revealed marrow edema.

Diagnosing sacral stress fractures is difficult because of the diversity of the differential diagnosis (Figure 1). Low back pain and generalized hip pain is common in patients and is usually related to soft tissue. For this reason, physicians do not often request radiographic tests when patients first present with these types of symptoms.25 In the present case, the patient was initially treated for piriformis or gluteus maximus muscle strain and leg length discrepancy. Likewise, in 42 of the 60 reported cases, patients with sacral stress fractures did not respond to initial treatment including rehabilitation, reduction of activity, or non-steroidal anti-inflammatory drugs. For the patient in the present case and for these 42 cases described in the literature, diagnostic imaging was eventually warranted and the stress fracture was detected.

Sacral stress fractures appear to be most common in individuals who participate in repetitive load-bearing activities.26 Sacral stress fractures are likely to occur because of changes in volume of training, shoe type, or terrain, in addition to factors such as fatigue and amenorrhea in women.26 The patient discussed in the present case did not report changes in shoe type or terrain, but he did report an increase in his volume of training. Inflexibility, as demonstrated by the presence of tight external rotator muscles on the patient's right side, may also have been a culprit in the denouement of this injury.

According to the literature, 57 of 60 patients had a history of load-bearing activity before presenting with a sacral stress fracture (Table 1). These findings suggest that a standard evaluation procedure for individuals who participate in repetitive load-bearing activities may be appropriate. An individual with low back and buttocks pain who participates in such activities should be strongly considered for screening for sacral stress fractures and other injuries of the spine and pelvis. Many individuals with sacral stress fractures described in the medical literature also presented with a history of concomitant stress fractures in the lower extremities.25-28

In 26 cases described in the literature, physical examination indicated low back and sacroiliac joint tenderness with unremarkable findings in the surrounding soft tissues (12 cases in the literature did not indicate whether palpation of surrounding soft tissue was included in the physical examination). Neurologic examination findings were typically normal, and patients demonstrated full, active range of motion, with some discomfort with passive hip flexion. Patients who present with this history and these physical examination findings should be asked to perform the hop test to recreate the load-bearing activity. Pain elicited by the hop test along with these other symptoms should be an indication to perform a bone scintigraphy or MRI. Radiography of the lumbosacral region may be useful to eliminate other causes of back pain but is not typically useful in diagnosing sacral stress fractures.29

Our review of the literature revealed that 6 women who participated in repetitive load-bearing activities and who reduced their caloric intake to lose weight with resultant amenorrhea had losses of bone mineral density that were noted in results of bone densitometry.11,12 This complication could have contributed to sacral stress fractures.

The management of sacral stress fractures is similar to the management of other stress fractures: remove the individual from activity and reduce load-bearing activity on the affected area. If a sacral stress fracture is diagnosed early, the patient may benefit from crutches to reduce pressure on the sacrum. However, because the stress fracture of the patient described in the present report was not diagnosed until approximately 2 weeks after onset of symptoms with cessation of activity, crutches were not recommended. The patient was instructed to take over-the-counter calcium and vitamin D supplements to increase bone formation and speed healing, which may be particularly important in women, who may be more prone to bone loss.11,12

Conclusion

Although sacral stress fractures are considered uncommon in the general population, individuals who engage in repeated load-bearing activities may be more prone to this injury. The similarities among the present case and the 60 cases of sacral stress fractures reported in the literature suggest a typical presentation for patients with this uncommon injury. We recommend that patients who present with lower back pain, diffuse buttocks pain, and a history of repetitive loading activity and who do not respond to standard treatments should be initially evaluated for sacral fractures (Figure 2). We also recommend treatment regimens that include 4 to 6 weeks of rest with gradual return to activity. A standardized evaluation and treatment plan for patients with symptoms of sacral stress fractures could lead to a quicker diagnosis and recovery. Continued research in sacral stress fractures may be warranted to delineate whether this injury is more common than currently reported.1